The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Little penguin wardens step up for big job

The big-hearted wardens of Sydney's endangered little penguin colony are hoping for the pitter-patter of tiny happy feet this breeding season.

Volunteers spent 1800 hours protecting about 40 breeding pairs from predators at North Head in Manly last year - the only known mainland NSW breeding ground for the smallest of the penguin species.

More than 50 people will rise to the challenge again this year, waiting patiently for the seabirds in critical habit areas and around Manly wharf, NSW Environment Minister Gabrielle Upton says.

"Last year's breeding season was a success because of the community's and National Parks and Wildlife Service's concerted effort to keep the penguins safe from predators," Ms Upton said in a statement on Thursday.

The little black penguins waddle into the area to get cosy between May and February, according to NPWS.

The males turn up first to prepare suitable burrows for their maidens, with peak breeding starting in July.

"The volunteers stay near the nesting boxes where there are known breeding birds, sitting quietly and making sure the penguins get home safely at night," a NPWS spokeswoman told AAP on Thursday.

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"They come back in the morning to check the penguins got out again safely."

The volunteers protect the colony from wild threats, such as foxes, until the end of summer while $300 on-the-spot fines will be given to people walking dogs in critical areas around Store, Collins and Quarantine beaches at any time.

Wardens will also be stationed at beaches to advise visitors they're closed after sunset.

Anyone who finds an injured or dead penguin around North Head is urged to report it to the NPWS duty officer.

A baby penguin took RSPCA inspectors by surprise in December when it was found trapped in a drain in Haberfield, in Sydney's inner-west. The youngster was examined at Taronga Zoo and later released into the wild.

Aside from the mainland, little penguins also breed in more than 10 island sites across NSW including Lion Island in Broken Bay and Five Islands Nature Reserve off the Illawarra coast.